Acid-activated bentonite (Maghnite-$\hbox {H}^{+})$ as a novel catalyst for the polymerization of decamethylcyclopentasiloxane

Abstract

In this study, we propose Maghnite-$\hbox {H}^{+}$, as an ecological, cost-effective and easily renewable catalyst, for the polymerization of decamethylcyclopentasiloxane (D5). The Maghnite is a clay consisting primarily of smectite minerals (montmorillonite group), which can be activated/reactivated through a simple process, by replacing interlayer cations by protons. Linear polymers with higher molecular mass and narrower molecular mass distribution (MMD) can be obtained with less cyclic by-products, using Maghnite-$\hbox {H}^{+}$. The reaction was investigated in bulk, taking into account the effect of time, temperature and amount of catalyst on the monomer conversion and MMD. When the yield rises to 96%, the MMD is broadened, suggesting the formation of cyclic oligomers and/or crosslinking bonds, this was confirmed experimentally by infra-red spectroscopy, proton nuclear magnetic resonance ($^{1}\hbox {H}$ NMR) and $^{13}\hbox {C}$ NMR analyses. The kinetics have been also studied; the reaction is first order in the monomer. The proposed reaction mechanism shows clearly the role of Maghnite-$\hbox {H}^{+}$ for D5 polymerization.